The transmission of a signal in a multi-path environment results in a plurality of delayed versions of the signal being received by receiving circuitry. Such multi-path environments are for example the result of obstacles in the path between the transmitter and the receiver, such as buildings, features of the landscape, etc.
Circuits for receiving signals in multi-path environments generally comprise a channel equalizer for summing all of the received signals and recovering the original signal. Such channel equalizers generally comprise a filter having many taps, often as many as several thousand. Each tap multiplies a delayed version of the input signal by a certain coefficient, and the outputs from all of the taps are added together to generate an output signal. The coefficients of the taps are generally calibrated for a particular environment at the start of a transmission, and may require recalibration at regular intervals, particularly in the case of dynamic transmission channels.
It is often difficult to calibrate the filter coefficients sufficiently quickly, particular at low signal to noise ratios. There is thus a need for an improved method and circuitry for determining the coefficients of the filter of a channel equalizer.